What are the effects of octanoic acid (OA) on acoustic, perceptual, and functional aspects of essential voice tremor (EVT)?
Magnitude of amplitude tremor (MATR) and magnitude of frequency tremor (MFTR) were significantly lower after three weeks of OA dosing compared to placebo. The results support the potential utility of OA for reducing the magnitude of tremor in people with EVT.
Background: The voice is affected in 20% to 30% of people with essential tremor. People with EVT experience unstable, shaky, and hoarse voice quality, increased effort with speaking, decreased speech intelligibility, and pronounced voice-related disability. Treatment options (botulinum toxin A) are inadequate for improving voice in EVT patients, but studies have shown that OA can reduce tremor severity in the hands by as much as 41%.
Study design: Prospective, double-blind, placebo-controlled, crossover study of 16 participants with an EVT diagnosis randomized to a three-week dosing condition of OA or placebo, followed by a two-week washout period and crossover to the other condition for an additional three weeks.
Setting: Department of Communication Sciences and Disorders, Syracuse University, Syracuse, N.Y.
Synopsis: A significantly lower MATR was seen after OA (baseline to post-test reduction of 4.14) when compared with placebo (0.48 reduction; 11 of 16 participants showed a >10% reduction of their baseline mean in MATR upon post-testing). Likewise, MFTR was significantly lower after OA (baseline to post-test reduction of 1.21) compared to placebo (0.22 reduction). Ten of 16 participants showed a >10% reduction of their baseline mean in MFTR upon post-testing. Sustained vowel ratings showed trends toward improvement after OA, but not for the all-voiced sentence ratings or self-perceived voice handicap. Analysis for higher OA dosing was completed for 14 participants, but none showed significant differences for primary or secondary outcome measures. No participants showed any indication of adverse medical effects on ECG and HFP results. One nonserious adverse event resulting in early study termination was later found to be related to a preexisting medical condition. Mean severity of symptoms ranged between minimal and mild levels for both placebo and OA.
Citation: Lowell SY, Kelley RT, Monahan M, et al. The effect of octanoic acid on essential voice tremor: a double-blind, placebo-controlled study. Laryngoscope. 2019;129:1882–1890.